Single wedge femoral stem designs are associated with a higher risk for revision after cementless primary total hip arthroplasty

Cementless total hip arthroplasty (THA) femoral stems are the most commonly selected prostheses in the United States (US). Optimal stem geometry remains controversial with excellent survivorship reported for many designs. We compared cause-specific stem revision of single-wedge versus double-wedge designs from a multi-center US cohort.Data from an integrated healthcare network's total joint replacement registry was used to conduct a cohort study. Primary elective cementless THA were identified (2001 to 2018). Implant exposure groups were classified by design geometry using the system proposed by Khanuja et. al. Type 1 single-wedge (n=11,082) and type 2 double-wedge (n=32,380) designs were compared, and other design types were excluded; the final study cohort comprised 43,462 THA. Cause-specific multivariable Cox regressions were used to evaluate risk for revision due to infection or aseptic reasons, including loosening, instability, periprosthetic fracture, or other reasons.After adjustment for covariates, a higher aseptic revision risk was observed for type 1 when compared to type 2 designs (hazard ratio [HR]=1.91, 95% confidence interval [CI]=1.33-2.75). When looking at specific revision reasons, revision for aseptic loosening (HR=3.46, 95% CI=2.24-5.34), was higher for type 1 versus type 2 designs. No differences were found for septic revision, instability, periprosthetic fracture, or revisions for other reasons.Type 1 single wedge designs were found to have a higher risk of revision due to aseptic loosening relative to type 2 double wedge designs. Femoral stem geometry should be considered when selecting a cementless femoral implant.